Merck:/Freestyle/LE-Lab-Essentials/Chromatography/LE-Lichrolut-150x210-05062014.jpgThe goal of solid-phase extraction is the selective isolation of target analytes from a complex sample or much larger sample volume prior to chromatographic analysis (e.g. HPLC, GC, TLC). As solid-phase extraction works on the principle of liquid chromatography, Merck Millipore’s LiChrolut® columns use strong but reversible interactions between the analyte and surface of the stationary. Typical interactions include hydrophobic (Van-der-Waals forces), polar (hydrogen bonding, dipole-dipole forces) or ion exchange interactions. Since interactions between the stationary phase and matrix should not occur, it is important to perform appropriate sample pretreatment. This allows the difference in chemical properties between the analyte and matrix components to be emphasized by altering the pH or the ionic strength of the sample solution. Under these conditions, the analyte is enriched as a narrow zone on the stationary phase. Subsequent to a washing step, which serves to remove possible adsorbed sample components, selective elution of the analytes can occur.